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    <title>Document</title>
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<script>
    var arr = [1, 22, 3, 4, 22];
    // 1-1;[1,2,3]
    // 1-2;new Array("1","2");
    // 2;长度控制
    // arr.length = 0;
    // arr.length = 1;
    // arr.length = conunt +1;
    // 3;数组检测
    // var res = Array.isArray(arr);
    // var res2 = arr instanceof Array;
    for (v of arr) {
        v + "@"
    }
    debugger
</script>

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